Titanium dioxide has stable physical property and chemical property, excellent optical property and electrical property, and good pigment property, and can be widely used in various applications. Titanium dioxide has found its use in fields of paintings, plastics, rubbers, chemical fibers, paper manufacture, inks, cosmetics, toys, capacitors, display tubes, sophisticated national defense technology, foods, medicines, chemical reagents, welding electrodes, enamels, ceramics, glasses, refractory materials, metallurgy, artificial gemstones, art pigments, leathers, printing and dyeing pastes, soaps, catalysts and so on
At present, the methods for preparing titanium dioxide mainly comprise chlorination process and sulfuric acid process.
The chlorination process has the advantages of advanced technology, short process flow, easily-realized automation and good product quality. However, the chlorination process puts high demands on the raw material quality and needs to use the rutile ore as the raw material which is a scarce resource. Besides, the chlorination process has technical difficulties because the materials and apparatus which are resistant to titanium tetrachloride, chlorine gas and oxygen gas should be applied when preparing titanium dioxide by the chlorination process. However, such materials and apparatus have high investment cost and difficulty in maintenance.
The sulfuric acid process has the advantages of cheap raw materials, mature process and simple apparatus. However, the process flow is long, the energy consumption is high, the amount of discharged wastes is large and the quality of product is poor.
At present, there are 47 plants which have a productive capacity of titanium dioxide of 30,000 to 150,000 tons per year in domestic, and the total productive capacity thereof is 3,500,000 tons per year. In these plants, only one plant uses the chlorination process to produce titanium dioxide, and the other plants all apply the sulfuric acid process for producing titanium dioxide. Nevertheless, these plants are still in a state of break even or under deficit due to their excess capacity of production.
Thus, how to obtain nanometer titanium dioxide with high quality under low cost is becoming a technical problem to be solved in the art.